The chemistry of the human body is responsive to an internal clock, which is independent of the timing of external conditions. Thus, when travelers fly over several time zones, their internal clock is upset by the change in environmental conditions, and they often experience difficulty in adjusting to the changing environmental conditions.
Their internal clock is out of sync with external environmental conditions, such as daylight and darkness. This difficulty in adjusting to changing environmental conditions is also present during seasonal changes in the environment.
In the Summer, the sun usually rises between 5:00 and 5:30 A.M. in North America. At dawn, the light intensity increases very gradually, gently arousing a sleeper in a restful manner.
In Winter, the sun usually rises between 7:00 and 7:30 A.M. in North America, and many people must awaken in the darkness, and transition from darkness to light is abrupt when a light is turned on. It has been observed that awaking in the summer months in response to the gradual increase in light from the sun leaves the human body and mind much more alert and with an overall good feeling. Quite the opposite effect occurs in the Winter months.
In addition to the effect of light on wakefulness, there is also a positive effect on one's mental state in the presence of a pleasant background sound, such as ocean waves or soft music. A positive effect is also generated by a pleasing aroma, such as the aroma of brewing coffee or freshly baked food.
Attempts have been made to provide artificial sunrise effects by mechanical or electro-mechanical devices. Several such devices are disclosed in U.S. Pat. Nos. 4,379,232, 4,038,561 and 3,727,395.
Alarm clock devices are well known in the art, which actuate an audio device, such as a clock radio or buzzer. Such devices are actuated from an "off" to an "on" condition, causing an abrupt change in the sleeping environment. While most clock radios are equipped with a volume control, the sound is not gradually increased over time as disclosed herein. Rather, the sound level is preset, and the audio device is actuated to the preset volume abruptly as the device is turned on.